Engine starter drive



Dec. 9, 1952 J. J. DIGBY 2,620,671

ENGINE STARTER DRIVE Filed Oct. 17, 1951 IN V EN TOR.

BY $172426 06/ WITNESS:

Patentecl Dec. 9, 1952 ENGINE STARTER DRIVE James J. Digby, Elmira, N. Y., assignor to Bendix Aviation Corporation, a corporation of Delaware Application October 17, 1951, Serial No. 251,771

3 Claims.

The present invention relates to an engine starter drive and more particularly to starter gearing of the automatically traversing type having "anti-kickout or "follow-through characteristics.

It is an object of the present invention to provide a novel engine starter drive which is selfcontained in that it requires no external stop for the pinion, and which is small and. compact in comparison with standard forms of drives having like torque capacity. I

It is another object to provide such a device incorporating a dental type of overrunning clutch, with. cam means for compressing the clutch members during cranking.

Further objects and advantages will be apparent from the following description taken in connection with the accompanying drawing in which:

Fig. l is a side elevation partly broken away and in section, showing a preferred embodiment of the invention with the parts in idle position;

Fig. 2 is a view similar to Fig. 1 showing the parts in cranking position; and

Fig. 3 is a similar view showing the parts in the positions assumed when the engine becomes selfoperative while the drive pinion is held in mesh with the engine ring gear.

In Fig. 1 of the drawing there is illustrated a power shaft l on which a driving head 2 is fixedly mounted by any suitable means as indicated at 3.

' A sleeve 4 having a terminal flange is rigidly mounted in a counterbore of the driving head 2 as by means of brazing as indicated at 6, and a driven head 1 is journaled on the sleeve, preferably separated from the driving head by a thrust washer 8.

Means for yieldingly connecting the driving and driven heads is provided comprising anchor plates 9 and II and non-rotatably mounted on the driving and driven heads respectively and connected by torsion spring I2, the ends of which are hooked into slots in the anchor plates.

A screw shaft I3 is mounted on the flanged sleeve 4 adjacent to the driven head 1, and is coupled to the driven head by means of interengaging projections I4, l5, which are maintained in engagement by the flange 5 of sleeve 4, which flange is formed after assembly of the screw shaft on the sleeve.

A control nut I6 is threaded on the screw shaft and is provided with inclined coupling teeth I! adapted to cooperate with similar teeth 18 on a cylindrical transmission member l9 which is rotatably mounted on the screw shaft. Transmission member is has overrunning clutch teeth 2| which cooperate with similar teeth 22 on a driven overrunning clutch member 23 which is splined as indicated at 24 on the extended hub of a pinion 25 journaled on the power shaft "I and moveable thereon into and out of engagement with an engine gear 26. The driven clutch member 23 is retained on the pinion hub by a split lock 21, against which the clutch member is pressed by a mesh-enforcing spring 28'bearing against the clutch member and a shoulder 29 on the pinion. The spring and splined connection are preferably enclosed by a sleeve 3| which is slidable on the pinion. f

A barrel member 32 is mounted on the control nut l6 and driven clutch member 23, and is provided with a flange 33 at one end which bears against the driven clutch member '23 and also against a flange 34 on the sleeve 3|. A lock ring 35 is located in the opposite end of the barrel"? and bears against the control nut I6 so as to limit longitudinal movement of the control nut, transmission member l9 and driven clutch member 23. Torque transmitted from the control nut through these associated parts thus causes the wedging action of the inclined teeth l1, l8 to compress the overrunning clutch teeth 2|, 22.

A detent member 36 is mounted in the control nut l6 for radial sliding movement, and a spring 3'! normally urges the detent against the surface of the screw shaft l3. The screw shaft is provided with a portion 38 of reduced diameter adjacent the position of the detent when the pinion is meshed with the engine ring gear. The shoulder 39 so formed on the screw shaft cooperates with the detent to resist demeshing movement of the pinion until the pressure of the detent against the screw shaft is relieved by centrifugal force caused by rapid rotation of the control nut.

In order to define the meshing position of the pinion 25, the travel of the control nut is on the screw shaft I3 is arrested by means of abutments 4| formed on the abrupt termination of the thread grooves in the screw shaft. The longitudinal movement of the control nut in the demeshing direction is arrested by engagement of a lug 42 on the control nut with a back stop 43 formed on the driven head. I. v

A ring 44 having a flange 45 is loosely mounted on the control nut and transmission member so as to enclose the inclined teeth I1, 18, and a light compression spring 46 bearing at one end against the flange 45 and at its other end against a rib 41 on the transmission member serves to normal- 1y maintain the clutch teeth 2i, 22 in engagement.

In operation, and starting with the parts in the positions illustrated in Fig. l, rotation of the power shaft l in the direction of the arrow causes the control nut it with the barrel 32 and associated parts to be traversed to the right in Fig. 1 until the pinion25 is meshed with the engine gear 26,. atwhich time the meshing movement is stopped by the engagement of the control nut with the abutments M on the screw shaft l3,

whereupon the pinion is rotated to crank the engine, the application of the load being cushionedby the torsion spring l2.

During cranking, the camm'ingaction of the inclined teeth l1, l8 forces the overrunning clutch teeth 2|, 22 tightly together so as toform.

a rigid driving connection. When the engine starts, the acceleration of the pinion 25'relieves the pressure of the cam teeth, permitting the pinion and clutch member 23 to overrun the transmission member 19.

Demeshing. of the pinion from the engine gear 26. is. at first prevented by engagement of the detent .36 with the. shoulder 39 on the screw shaft, so, that if the engine does not remain self-operative, the clutch teeth 2], 22 will be reengaged by thespring lfiand. cranking resumed. When the engine continues self-operative, the acceleration of the control nut by the starting motor, and by the torque transmitted back from the overrunningpinion, causes the. detent 36 to be withdrawn by centrifugal force, permitting the parts to be returned to idle position by the torquefrom the pinion as controlled by the clutch spring 45.

Although butone embodiment of the invention has been shown .anddescribed inv detail, it will be understood that. various. changes may be made in the. precise design and arrangement of the parts withoutdeparting from the spirit of the invention.

I claim:

1. In an engine starter drive, a power shaft, a driving head fixed thereon, a flanged sleeve on the shaft rigidly attached at one end to the driving head, a driven head journaled on the sleeve, means including a torsion spring yieldingly connecting the driving and driven heads, a screw shaftv mounted .on the. sleevehaving a. positive coupling connection with the driven. head which is maintained by the engagement of the flange on the sleeve with the free end of the screw shaft; a control nut on the screw shaft having inclined coupling teeth, a cylindrical transmission member havingsimilar coupling teeth at one end cooperating with-those of the control nut, and having overrunning clutch teeth on its other end; a pinion slidably journaled on the power shaft for d riving engag-ement with an engine gear, a driven overrun-ning clutch member splined on the pinion, and means including a barrel member enclosing the control nut, transmission member and clutch memberand limiting their'relative longitudinal movement, so that the wedging action of the-"inclined coupling. teeth compresses the overrunning clutch connection;

2. An engine starter drive as set forth in claim '1 in which the threads of the screw shaft terminate abruptly to form. abutments which arrest the-meshing movementofthe control nut.

3. An engine starter drive asset forth in claim lincluding further a detent mounted in the control nut for radial movement, a' spring normally urging the detent into engagement with the screw shaft, said 'screwshaft having a shoulder in position to be engaged by the detent to oppose demeshing movement of the'control nut.

JAMES J. DIGBY.

No references cited. 

